Araki Nobukazu
Department of Histology and Cell Biology, School of Medicine, Kagawa University, Miki, Kagawa 761-0793, Japan.
Front Biosci. 2006 May 1;11:1479-90. doi: 10.2741/1897.
Microtubules serve as tracks for vesicular traffic in both phagosome formation and phagosome maturation. In the process of phagosome formation, endomembrane vesicles are delivered to the membrane of the forming phagosomes to supply membrane. This localized endomembrane delivery, referred to as focal exocytosis, facilitates pseudopod extension for the purpose of engulfing large particles. The microtubule-based transport system is the most likely candidate for such targeted vesicle trafficking to the forming phagosomes. During their maturation process, phagosomes interact with early and late endosomes and finally fuse with lysosomes. Although phagosomal membrane fusion with other membranous compartments does not require microtubules, bi-directional transport and positioning of the two organelles on microtubules are necessary for their close positioning and subsequent membrane fusion. Microtubules are also responsible for vesicle trafficking along the antigen presentation pathway for phagocytosed materials. Some classes of myosin are involved in diverse processes of Fc gamma receptor (FcgR)-mediated phagocytosis as force generators and actin-based transport motors. The role of myosin II in phagocytic cup squeezing is complementary to the classical zipper closure model. Myosin Ic and myosin X seem to be key players in extending and closing phagocytic-cup pseudopod. Other classes of myosin may also be involved in phagosomal movement. Myosin V may control short-range phagosome movement and relay phagosomes to the long-range linear transport system using microtubules.
微管在吞噬体形成和吞噬体成熟过程中均作为囊泡运输的轨道。在吞噬体形成过程中，内膜囊泡被递送至正在形成的吞噬体膜，以提供膜成分。这种局部内膜递送，即局灶性胞吐作用，有助于伪足伸展以吞噬大颗粒。基于微管的运输系统是这种靶向囊泡运输至正在形成的吞噬体的最可能候选者。在其成熟过程中，吞噬体与早期和晚期内体相互作用，最终与溶酶体融合。尽管吞噬体膜与其他膜性区室的融合不需要微管，但这两个细胞器在微管上的双向运输和定位对于它们的紧密定位及随后的膜融合是必要的。微管还负责沿吞噬物质的抗原呈递途径进行囊泡运输。某些类型的肌球蛋白作为力产生器和基于肌动蛋白的运输马达，参与Fcγ受体（FcgR）介导的吞噬作用的多种过程。肌球蛋白II在吞噬杯挤压中的作用与经典的拉链闭合模型互补。肌球蛋白Ic和肌球蛋白X似乎是伸展和闭合吞噬杯伪足的关键参与者。其他类型的肌球蛋白也可能参与吞噬体运动。肌球蛋白V可能控制吞噬体的短程运动，并将吞噬体传递至使用微管的长程线性运输系统。
